In view of the prior-art technology of the pneumatic tools, the air flow controlled by the rotation speed of a rotor in a control chamber is a well-known art. At present, there are different structural designs for the air intake adjusting assembly, and most traditional air intake adjusting assemblies use a screw rod 11a to change the air flowing into a chamber as shown in FIGS. 1 and 2. By rotating the screw rod 11a into or out from a main body 10a, the diameter of an air intake passage 13a is decreased or increased as to adjust the flow of air entering from the air intake section 12a. However, the air intake adjusting assembly according to such technology is installed into a chamber interconnected to the main body 10a. When a driving device 14a is pressed to operate a pneumatic tool, the air intake adjusting assembly will be covered. Such result not only makes the grip uncomfortable to users, but also makes the adjustment of the air flow impossible. Therefore, it is necessary to stop operating the pneumatic tool first before making adjustments by the air intake adjusting assembly, which is very inconvenient to users. Further, since it is unable to simultaneously operate the pneumatic tool and the air intake adjusting assembly, therefore the air flow cannot be adjusted precisely. Users have to stop operating the pneumatic tool and rotate the screw rod 11a into or out from the main body 10a of the pneumatic tool and then test the pneumatic tool to check whether or not the air flow of the entering air is appropriate. This procedure is repeated until the air flow is adjusted to the desired level, and the procedure of adjusting the air intake adjusting assembly wastes a lot of time. Furthermore, since the air intake adjusting assembly is disposed at the main body 10a, therefore the screw rod 11a will be touched very easily during the operation of the pneumatic tool and thus the screw rod 11a will be driven to rotate and change the flow of the air intake and definitely will affect the operation of the pneumatic tool.